Flywheel

[Aethelric]

This might help:

http://www.bmwr65.org/YaBB2.612/cgi-bin/yabb2/YaBB.pl?num=1446449519

Thanks for that. So it's rare but not unknown. 
I'm just waiting for my flywheel and associated single use bolts to arrive now.

I'm not a one for fixing anything that ain't broke "while I'm in there". The bike has only done 45,000 miles, the clutch plate measures 5.16mm thickness, (new 6mm, BMW recommended limit 3.5mm)

[georgesgiralt]

I, for one, would be glad to know how this crown has sheared it's rivets. What kind of steel they used at Sachs ? Bubble gum ?
It is very strange but not unheard of but it is the first time I see pictures of it.

[Aethelric]

Some of the holes in the ring gear look slightly oval now. I suspect that the ring has been rattling backwards and forwards a few thou for quite a while and this has finally resulted in failure by metal fatigue.



For the last 100 miles or so I could hear a noise which sounded to me like the timing chain.  So I changed it.  In hindsight this was a waste of effort and money as the old components were fine.  The noise was probably the ring gear rattling. 

[Tony Smith]

Has anyone else come across this?

The starter ring fell off my flywheel (well clutch carrier to buy into BMW "Newspeak" a couple of years back - symptoms were near identical to what you describe.

It turns out that this is a sufficiently frequent occurance that sellers of 2nd had partsa think that their offerings are made of solid gold.

It is also the case that BMW had a couple of goes at using different size/composition rivets and that only the most recent ones appear to be immune.

On the basis of the prices demanded by wreckers and not wanting to have to deal with the matter again, I bought a new one.

Don't forget to mark your clutch pack so that it goes back with the same relative positions.

Also not a bad idea to replace oil pump deal and rear main seal whilst you are there, along with the gearbox input shaft seal.

Getting the gearbox off and the flywheel out is not a job you want to do too often.

[Aethelric]

Thanks Tony - I did see your post about it. 
I ordered a new flywheel, but they were not in stock and Motorworks were unsure about delivery due the the current virus conditions here in plague central.  So I changed the order to a second hand one.  £75 as opposed to £165 + VAT.

I found the original paint marks on the clutch parts and the replacement flywheel and put them in 120 degrees apart.

It's fitted back on now, together with the clutch.  I decided against replacing seals, just to minimise time and effort. I hope this doesn't come back to bite me. My experience of "I'll just do this while I'm in there" always seems to lead to unexpected problems.

I should get the gearbox back in over the next few days.

[Aethelric]

Replacement fly wheel fitted.   My torque wrench only goes up to 50ft lb and I needed 80.  So a two foot lever and a luggage scale was used to measure 42 lbs.  (The extra 2lb was the weight of the lever)

Clutch fitted using a home made clutch centering tool, which must have worked OK as the gearbox is fitted now.

[Aethelric]

All back together now.
It took a little longer than expected as I dropped a drive coupling bolt into the drive shaft housing.  So I had to take the entire back wheel and swinging arm of to tip it out (along with the drive shaft oil over the garage floor).
I took it out for a 20 mile test run, and it feels fine, and no rattles!